High speed solenoid employing multiple springs

TLDR: A high speed solenoid assembly especially adapted for use in impact printers of the dot matrix type is described in this article, where the authors use a headed armature with a depression along its rear surface to reduce the armature "bounce".

Abstract: A high speed solenoid assembly especially adapted for use in impact printers of the dot matrix type The solenoid coil, when energized, drives the solenoid armature and a print wire connected thereto for impact against an inked ribbon and paper document to form a dot upon the paper document The armature is initially driven against the biasing force of a "weak" spring to facilitate rapid acceleration to impact velocity Just before the print wire strikes the inked ribbon and paper document, the armature comes under the influence of a "kicker" spring having a greater spring force and which is flexed by the moving armature which serves to return the armature to the non-impact position at a more rapid rate when the solenoid coil is deenergized The use of a headed armature with a depression along its rear surface serves to significantly reduce armature "bounce" The assembly significantly reduces elapsed time between movement of the armature and print wire from the rest position to the impact position and return of the armature to the rest position enabling significantly increased printing speeds